Disk for sound boxes



'Patented Jan.' 1, 1929.

UNITED lSTATES lPMENT QFFICE.

OTTO R. GRSS, OFGHICAGO, ILLINOIS, SSIGNOR T0 ORO-TONE COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION 0F ILLINOIS.l

DISK FOR SOUND BOXES.

Application led March 27, 1926. Serial No. 97,833.

My invention relates to diaphragms for sound boxes for talking machines and method of making same and has for its primary object the provision of a diaphragm having an annular extending area of iexure therein formed by reducing the thickness of the diaphragm by machining the diaphragm around its margin and thereafter forming as an addition` thereto, an annular stiffening ribl on said diaphragm adjacent the cut-away portion, and also offsetting a portion of the cut-away portion thus providing a d1aphragm having a circular extending area of 'fiex'ure adjacent the edge of the diaphragm Where it is secured to the sound box, thus producing a diaphragm which is bodily movable from a point near the outer edge thereof, thus reproducing the sounds in a. very much clearer and better manner than what has been possible to accomplish heretofore, and also doing away with the blasting sound so com' mon in the reproductions of music, speech or sound from a phonograph record.

A further object of my invention is the provision of a diaphragm in which the outer edge of the diaphragm is reduced to a mini'- mum thickness by machining so that the area of flexure of the diaphragm is uniform throughout its entire portion thereby resulting in a substantial equal body7 movement of the free portion of the diaphragm in the sound box.

As is well known in the phonograph art, in

order-to obtain tones which are clear and in .which the reproduction'thereof is as n ear the natural tone of the voice or instrument from which the tone was originally recorded, it is necessary to have the entire body portion of the diaphragm vibrate so that the movement of vibration of the diaphragm is as great at the outer portion of the diaphragm as itis in the middle of the diaphragm or at the point to which the stylus bar is attached or substantially so. vIf a diaphragm of equal thickness is produced throughout its entire areaand secured in the sound box around its A outer marginal edges of ordinary construction, the greatest movement of the diaphragm will be at the point Where the stylus bar'is secured to the diaphragm, usually at the fcentral point thereof, and the amount. of movement of the diaphragm or flexure thereof will decrease .from the cent-ral point 'out to the In my improved structure I e central vibratory move- `seek to redud;

ment of the diaphragm to a minimum and secure a body movement of the unattached or free portions of the diaphragm by produclng a diaphragm having the outer edges machmed to aminimum degree of thinness consistent with strength and produce in the central portion of the diaphragm a pair of concentric rings which serve to stien the central portion of the diaphragm and produce a diaphragm having an area of flexure around the outer edge adjacent the machined part of the diaphragm.

Another and further object of my inventron is the provision of a diaphragm which is simple in construction andV which is easy to manufacture and also in which the area of the exing p ortion of the diaphragm is positloned adjacent the outer ring or fastening point of the diaphragm.

Another and further object of my invention 1s the provision of a method of making diaphragms for sound boxes and in which the dlaphragm blank is machined on its outer margmal edge and then is pressed into the proper contour to ive a stiif body portion and have the area 0% flexure as near the outer marginal edge of the diaphragm as possible y after 1t 1s mounted in the sound box.

.These and other objects of my invention' will be more fully and better understood by reference to the accompanying sheet of drawings and in which Figure 1 is an elevational view of a blank used in making diaphragms for sound boxes;

' Figure 2 is a cross sectional view of the blank shown in Figure 1 I Figure 3 is an elevational view after the blank shown in Figure 2 has been machined ofi around its outer marginal edge;l

Figure 4 is a cross sectional view of the blank shown in Figure 3;

Figure 5 is an elevational view of the diaphragm after it has been pressed between a pair of molds and ready for insertion in the sound box;

Figure 6 is a cross sectional view of the diaphragm shown in. Figure 5; and

Figure 7 is a View partially in section and partially in elevation of a sound box showing my improved diaphragm mounted therein.

Referring now specifically to the drawings and in which like reference 'characters refer to like parts throughout, a disk 10 is shown which is a composition of various materials mately thirty thousandths of an inch such as rubber, Celluloid and the like, and which are producedin commercial quantities, the said disk being cut to any size desired and of uniform thickness throughout its entire area, the said blank being approxiin thickness throughout its entire area. In following my improved method, the blank 1Q is machined in any suitable manner`- (Figures 3 and 4) by cutting away -a portion of the blank 10 around the outer marginal edge fthereof and inward to a point somewhat further than necessary to provide an edge suiiicient for the? mounting of the diaphragm, thus producing a shoulder portion 11 which extends around the disk 10 and the outer portion 12, the said portion 12 being machined down to approximately five thousandths of anv inch in thickness.

After the operation just above described has been performed, the blank 10 is preferably placed between a pair of dies and the said dies are heated slightly and the dia-I phragm subjected to pressure so that an annular recess 13 is produced upon one side of the said diaphragm blank and preferably with an inner annular recess or groove 14 being produced with a corresponding rib .15 being produced on the outer side of the .diaphragm and with an annular/rib or ridge 16 being produced opposite the recess 13, the

said recess 13 being approximately double rection so that when the diaphragm is mounted in a sound box the point of i'lexure of the diaphragm is between the shoulder 11 and` the point 17 of the machined portion `12 or the diaphragm. A hole 18 is punched in the central portion of the diaphragm for. the pur-V pose of attaching the stylus bar to the diaphragm. l

As illustrated in Figure 7, `a sound box 1s shown and which comprises a base 19 havmg a collar 20 adapted to fit over the end of the usual tone arm and having a spring pressed ball 21 therein adaptedto hold the sound box in engagement upon the tone arm. A

threaded plug 22 is provided with a spring 23v which serves 'to hold the ball l21 in Vposition. A cover plate 24 is provided which is secured tothe portion 19'by means of screws 25, 25, the said cover plate having a stylus bar A26pivotal1y mounted thereon'inthe usual lmanner, the stylus bar 26 having a recess 27 therein within which the upper end of ance-A ,dle is'adapted to sit with a screw 28'adapted Leeaefie to hold the needle in position. The stylus bar is secured to the diaphragm 10 by means of a screw 29 which passes through the upper end of a stylus bar 26 and through thehole 18 in the central portion of the diaphragm 10. An annular member 30 is provided against which the portion 12 of the diaphragmv 10* rests with a second annular member 31, these members ordinarily being rubber covered so thatthe outermarginal edge 12 of the diaphragm 10 is compressed tightly between the members 30 and 31 when the sound box is assembled, as shown in Figure 7.

It will be thus understood that the blanks, as shown, which are approximately thirty thousandths of an inch in thickness, have the outer marginal edges reduced in thicknessby cutting away a portion of the disk to approxi'- mately live thousandths of an inch in thickness and thereupon the diaphragm is preferably placed in dies which are heated and thediaphragm molded into the condition shown -in Figure 6 and thus the body portion of the diaphragm is strengthened by means of the annular ribs 15 and 16'so that a point of flexure is provided in the diaphragm beginning at the point 17 and ending adjacent the shoulder 11 (Figure 6) and the diaphragm being so materially reduced in thickness and so thin, receives the vibrations from the stylus bar 26 enA and thus the plane of movement at the outer edge of the diaphragm is substantially equal to thelplane of movement of the diaphragm at the middle portion thereof where the stylus bar is joined'to the diaphragm. It will be further understood that while l prefer to form the diaphragm with the rib adjacent the cut-away portion, that this operation may be dispensed with and merely'by cutting away a portion of the diaphragm a uniform area of iexure 'is formed which has not heretofore been obtained in the manufacture of diaphragms.

While' I have described more or less precise-A lyth'e details of construction, l do not wish to be understood as limiting myself thereto, asl I contemplate changes in form and the proportion of parts and the substitution of equivalents as circumstances may .suggest or render expedient without departingfrom the spirit or scope of my invention.

I claim:

1. A diaphragm comprising a disk mate-l rially reduced in thickness on its outer periphery'and having a circular channel formed in oue-sideof said disk which partially includes the portion of said disk which is reduced in thickness, whereby an area` of em'bility is formed in said diaphragm adjacent the outer periphery thereof. 'Y

2 A diaphragm comprising a disk having e portion thereof reduced around its marginal Y edge on one side only, and a plurality of concentric ribsormed' therein on one side of ,said disk-.and aplur'ality of channels concentrically arranged on the opposite side ofsaid disk, the outer channel extending underneath the outer rib and into said cut away portion,

whereby an area of flexure is formed adjacent the outer periphery of the said diaphragm.

' 3. A diaphragm comprising a disk having a portion thereof materially reduced in thickness extending circumferentially around said disk and having an annular groove on one side thereof and a rib on the opposite side of said disk,said groove and rib being opposite each other, said rib being of lesser Width` than the said groove and spaced apart from the outer marginal edge of said disk whereby an area of fleXure is formed adjacent the outer periphery of the said disk.

4. A diaphragm comprising in combination ing an annular rib formed therein upon one side of said disk and an annular depression formed on the opposite side of lsaid disk of' greater Width than the said rib and having a portion thereof opposite the rib, said depression extending into the portion of said disk which is reduced in thickness whereby an annular arca of fiexure is formed on said disk adjacent its outer edge, and having a portion of said disk extending beyond the said area of flexur'e to provide means for mounting the said diaphragm in a sound box.

'Signed at Chicago, Illinois, this 20th day of March, 1926.

' OTTO R. GRASS. 

